This invention is concerned with an automobile provided with a catalytic converter in the exhaust line and relates to a precautionary measure against burning of an interior covering for the vehicle floor by an abnormal rise in the temperature of the catalytic converter.
Catalytic converters are widely used in automotive engine exhaust systems for the removal of carbon monoxide and hydrocarbons, and sometimes nitrogen oxides too, from the exhaust gas. Since exothermic oxidation reactions occur in a catalytic converter for this purpose, there occurs a significant rise in the temperature of the catalytic converter if a larger quantity of unburned fuel is introduced into the converter as the result of a certain trouble such as run-on of the engine, misfires in the engine or a failure of an acceleration pedal return mechanism. Since the catalytic converter is almost unexceptionally located beneath the floor of the vehicle body at a short distance, such an extraordinary temperature rise of the converter causes a significant heating of the floor in a region above the converter. Then there is a possibility, not merely suppositionally, that an interior covering for the floor such as a carpet which has a relatively low ignition point might be burned. The possibility of such accident is seen also when a thermal reactor or afterburner is employed in place of a catalytic converter, though the possibility is rather remote in this case.
To prevent this sort of accident, it has already been put into practice to provide a warning system which monitors the temperature of the catalytic converter and/or the floor to give a visual or auditory warning to the driver if occurs an abnormal temperature rise so that the driver may take a certain counter-measure. Furthermore, it is prevailing to provide a heat-shield plate above or around the catalytic converter so as to shield the vehicle floor from the heat the converter radiates.